Psychology we said deals with facts of consciousness, but this is too broad a statement, for there are other sciences that also deal with facts of consciousness, such as ethics, aesthetics, logic. In what respect does psychology differ from these sciences? It differs in this that ethics, aesthetics and logic are normative regulative sciences; psychology is a positive natural science. Ethics deals with ideals of moral life, aesthetics with ideals of beauty, and logic with ideal ways of correct reasoning. All these sciences deal with ideals, with norms to which the matter of fact consciousness ought to conform, if it is to act rightly. They put a value on the phenomena. Psychology, however, like all other natural sciences has no other ideal than fact, it admits of no "ought." From a strictly psychological standpoint, the ugly and the beautiful, the good and the evil, the true and the false are of equal value. Psychologically they are all facts of consciousness and must be studied as such; just as the serpent and the dove are of equal interest and value to the naturalist. The ravings of a maniac are of the same psychological interest and value as the subtle reasoning of a Newton. Psychology is a positive natural science, it does not deal with the subjective evaluation of facts of consciousness, but with their objective natural existence.

Having shown in what psychology agrees with other positive natural sciences, we must now point out in what it differs from them. Psychology deals with phenomena of consciousness as facts of objective natural existence. Are these facts of the same order with those of the physical world, the subject matter of the natural physical sciences? We must answer in the negative. The objects of the natural sciences of the physical world arc of a material and spatial nature. A physical body has weight, occupies a certain portion of space, so has the molecule, the atom. Can we say the same of psychological facts? By no means. They are different in kind, and this I wish especially to impress on the mind of the reader. To realize this truth, I think it a good preliminary psychological exercise for the reader to try to find how many grams, or grains his idea of beauty weighs, how many millimeters long, wide and high his feelings of love are; let him indulge in the fancy of conceiving an engineer building a bridge with mathematical formulae as links, and his feelings of virtue and patriotism as supports. On the other hand let him think of a logician trying to fill up the defects of his train of reasoning with solid bricks, and using as connecting links bars of pig iron. In short, psychology differs from physical sciences in this, that its facts, the facts of consciousness are not of a material nature.

"Do not physical sciences it may be asked "deal with such phenomena as sound and light?" Certainly they do, but these sciences regard these phenomena from a standpoint radically different from that of psychology. Sound in physics is not the sensation sound, but the external, material vibration of air, which may or may not give rise to a sensation of hearing. The same holds true in the case of light. What physics investigates is not light as sensation, but vibrations of ether which may or may not give rise to a sensation of sight. It is, however, just such facts as sensations, facts not spatial in their nature which constitute the subject matter of psychology.

"May not facts of consciousness be some kind of matter, some form of material substance the constitution of which we do not as yet know?" Such was the question put by a medical man, when he heard me expounding the difference in kind between physical and psychical facts. "That might be" I answered, "but then substance, if it ever be discovered, will not have the properties of matter; it will be a "matter" totally different in kind from that studied by the physicist. For the "matter" of physical sciences is essentially one of extension; a matter however that occupies no space is an existence altogether different in kind from that of extended things, and is certainly no "matter" for the physicist.

The persistent antagonist may raise here a further objection. "Are not the phenomena of consciousness" he may ask "facts of activity? And is not activity, kinetic energy? And if this be the case must not the facts of consciousness be ranged along with physical phenomena, be reduced to the manifestations and transformations of kinetic energy and thus really and ultimately fall within the domain of the mechanical sciences?"

Change certainly is manifested in the mutations of states of consciousness, but this change is not the physical change of translocation. Change in the states of consciousness may no doubt, be regarded as activity, and if you please as energy, but this activity is not the energy of mechanics. Activity in mechanical or physical sciences means molar, molecular, or atomic movement of matter through space, while psychic activity is not a translation of matter through space, a thought is not a material mass having extension, weight and locomotion. This truth, simple as it may appear, cannot be too often repeated and too strongly emphasized, since one frequently meets with this fallacy of "thought-materialization" in the world of psychiatry. Words are often misleading and the metaphorical expression "mental energy" is taken in its literal meaning of mechanical energy. While I am writing these lines I find in one of the number of the Russian "Archives of Psychiatry and Neurology" edited by Prof. Kowalevsky, an article, in which an attempt is made to express mental activity in terms of mechanical energy. The writer might as well attempt to change inches into pounds. He who undertakes the examination and study of mental phenomena must bear in mind the simple and important, but frequently forgotten truth, that facts of consciousness are not of a physical, mechanical character.

Against our view may be urged the fact that in proportion as a science tends to become exact, it takes on more a quantitative aspect, its phenomena are reduced to molecular or atomic changes. If now psychology is a science at all, it will reach its exactness, when it can be expressed in terms of matter and motion, so that the phenomena presented by consciousness, although at present impenetrable to our imperfect instruments and methods of investigation, must ultimately be reduced, in some way or other, to mechanical terms. Psychology has not yet had its Galileo.

This objection may be easily disposed of by the simple answer that the exactness of science is not at all in proportion to its degree of reduction to terms of matter and motion. No one will deny that mathematics is an exact science, but is it exact because it is reduced to mechanical terms? While mechanics must be logical, logic is not mechanical.

Within certain limits this generalization of the relation of scientific exactness to mechanical formulae may be fully granted, if it be restricted to the concrete physical sciences, but it cannot possibly hold good in case of psychology, as the latter does not fall within the circle of the physical sciences.

The weakness of this last objection from scientific exactness becomes clearly disclosed, if we get a little deeper into the matter. The reason why there is such a persistent tendency to reduce science to mechanical terms is based on the tacit understanding that atoms and motion are the only ultimate realities. We see at a glance that this consideration is at bottom purely metaphysical; it is a consideration which science has not to take into account. Nothing is so dogmatically metaphysical as just the common sense that has an abhorrence of metaphysics. That atoms and their motions are the only ultimate realities is certainly metaphysics and bad metaphysics too, as it is unguarded by reflective critical thought. Since this unreflective metaphysics of atomism is widely spread in the medical world, and is considered scientific, one cannot help discussing it, pointing out its deficiencies, showing up the obstacles it puts in the way of positive science. Metaphysics is a branch of philosophy which deals with the nature of reality. As philosophy it accepts no unanalyzed concepts; unlike science it has no postulates taken blindly on faith. The proposition now before us, namely that atoms and their motion are ultimate realities, is bad metaphysics, because it is a blind unanalyzed postulate. How do we know that atoms and their motions are ultimate realities? Why not ask what is reality? Once we are on metaphysical ground, why not take it in real earnest? Why stop on atoms and motions? Atoms themselves are not ultimate simple units, they have shape, size, weight. Now shape, size, weight, what are they after all? They are so many resultants of masses of factual, visual and muscular sensations, which are as little ultimate as are the sensations of color or of pain. It is out of sensations, percepts and ideas that the concept "atom" is framed. Subtract from the atom its sensational, perceptual and ideational elements, abstract from it its shape, size, weight and the ultimate reality of the atoms will become a bare nothing. The atom therefore is ultimately resolved into terms of consciousness. The same holds true in case of motion. Motion is a mental product of what is known as muscular and retinal sensations. What is most ultimately known is only consciousness and its facts. The atom and its motions are after all nothing else but constructs of consciousness. From the standpoint of epistemology, or what the Germans call "Erkenntnisstheorie," we have only a double series of mental phenomena, one standing for the internal and the other for the external world, and not atoms, but mental life may be regarded as the ultimate reality.

From a strictly scientific standpoint, however, we have no right to resolve matter into mind or still less mind into matter, because the two are presented to consciousness as different in kind, even though they both may belong to a general consciousness. Between the two series of facts, the physical and the psychical, there exists a fundamental difference. The door yonder is covered with white paint, the inkstand before me is made of glass, is round, is heavy, is black, but my idea of the door is not covered with white paint, my idea of the inkstand is neither made of glass, nor round, nor heavy, nor black. In short, the facts of consciousness are not spatial.

A fallacy prevalent among the medical profession and now also extant among the populace is the placing of psychic life in the brain. The neurologist, the pathologist ridicule the old Greek belief that the place of the mind is in the heart. Modern science has discovered that the heart is nothing but a hollow muscle, a blood pump at best, the place of mental processes is in the brain. This medical belief now circulating in the popular and semi-scientific literature of today differs but little from the ancient Greek belief, it is just as fallacious and superstitious. It is true that psychic life is a concomitant variable function of nervous processes and brain activity, but neurosis is not the cause of psychosis. The brain does not secrete thought as the liver secretes bile. The mind is not in the brain, nor in fact is the mind anywhere in the universe of space; for psychosis is not at all a physical spatial process.

As fallacious and superstitious is the recent tendency of medical investigation to localize psychic processes, to place different psychic processes in different seats or localities of the brain, thus implying that each psychic process respectively is placed inside some cerebral centre or nerve cells. Psychic life is no doubt the concomitant of nervous brain activity, and certain psychic processes may depend on definite local brain processes, but the given psychic process is not situated in a definite brain center, nor for that matter is it situated anywhere in space.